Updated

For the first time, Baltimore has topped pest control company Orkin’s list of top 50 cities with the most bed bug treatments, a ranking based on national home and commercial treatment data from Dec. 1, 2015 to Nov. 30, 2016.

Bed bugs— tiny, blood-sucking nuisances that can leave skin with itchy welts— travel easily and can reside even in clean homes, according to a news release by Orkin. Although painful, bed bug bites do not pose a serious medical threat, and those people who are bitten can find relief in antiseptic creams, lotions and antihistamines, according to the Centers for Disease Control and Prevention (CDC). To avoid irritating skin, the CDC advises against scratching bed bug bites.

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“Bed bugs only need blood to survive. We have treated for bed bugs in everything from million dollar homes to public housing,” Orkin Entomologist and Director of Technical Services Dr. Ron Harrison said in a news release.

Bed bugs were virtually unheard of 10 years ago, according to the company.

“We have more people affected by bed bugs in the United States now than ever before,” Harrison said in the release.

Four of the metro areas made Orkin’s rankings for the first time: Las Vegas, Portland, Salt Lake City and Greensboro-High Point-Winston Salem.

Here are the top US cities with the worst bed bug problem with their annual ranking changes from 2015 indicated in parentheses:

1.    Baltimore (+9)

2.    Washington, D.C. (+1)

3.    Chicago (-2)

4.    New York

5.    Columbus, Ohio

6.    Los Angeles (-4)

7.    Detroit

8.    Cincinnati

9.    Philadelphia (-3)

10. San Francisco-Oakland-San Jose (+4)

11. Richmond-Petersburg, Va. (-2)

12. Raleigh-Durham, N.C. (-1)

13. Cleveland-Akron-Canton, Ohio (-1)

14. Indianapolis (+1)

15. Dallas-Ft. Worth (-2)

16. Atlanta (+3)

17. Houston

18. Buffalo, N.Y. (+2)

19. Charlotte, N.C. (-3)

20. Norfolk-Portsmouth-Newport News, Va. (+10)

21. Knoxville, Tenn. (+3)

22. Denver (-4)

23. Nashville, Tenn. (-1)

24. Pittsburgh (+5)

25. Greenville-Spartanburg, S.C.-Asheville, N.C. (-4)

26. Phoenix (-3)

27. Grand Rapids-Kalamazoo-Battle Creek, Mich. (+5)

28. Boston (-3)

29. Milwaukee (-3)

30. Champaign-Springfield-Decatur, Ill. (+12)

31. Hartford-New Haven, Conn. (+3)

32. Dayton, Ohio (-4)

33. Omaha, Neb. (+3)

34. Seattle-Tacoma (-6)

35. Tampa-St. Petersburg, Fla. (-4)

36. Charleston-Huntington, W.Va. (-1)

37. St. Louis (+3)

38. Cedar Rapids-Waterloo-Dubuque, Iowa (+3)

39. Myrtle Beach-Florence, S.C. (+11)

40. Syracuse, N.Y. (+6)

41. Louisville, Ky. (-2)

42. Greensboro-High Point-Winston Salem, N.C.

43. Lexington, Ky. (-10)

44. Orlando-Daytona Beach-Melbourne, Fla. (-6)

45. Kansas City, Mo. (-1)

46. Miami-Ft. Lauderdale, Fla. (-3)

47. Salt Lake City, Utah

48. Honolulu, Hawaii

49. Las Vegas

50. Portland, Ore.